A need exists for high temperature, ultra-thin, polymeric film for aeronautics and space applications. A successful candidate material must be lightweight, thermally stable, flexible, and possess antistatic properties with an electrical resistivity of 10.sup.8 -10.sup.10 ohm-cm for the purpose of relieving space charging effects.
Linear aromatic polyimides are presently being considered as candidates for large space structural applications. However, a problem arises in that linear condensation polyimides are not electrically conductive by nature and possess an electrical resistivity of approximately 10.sup.17 ohm-cm.
Polymers which do conduct an electric current have received considerable attention in the chemical literature. Although a few polymeric systems such as (SN).sub.x, polyacetylene, and poly(p-phenylene) have conducting properties when complexed with electron donors or acceptors, the majority of polymers do not. One of the most common methods for imparting electrical conductivity into insulative polymers is the incorporation of conductive fillers. To date fillers have been introduced at rather high concentrations and are primarily particulate in nature such as metals, carbon fibers or spheres. Attempts at lowering the resistivity of polyimide films have been made by doping the polymers with metals such as aluminum or with carbon microspheres. Such attempts, however, have unfortunately led to an unwanted increase in the weight of the material, a much embrittled film, uneven dispersion of metal throughout the film and a degradation in thermal and mechanical properties.
The doping of polymers with metal "ions" has received little attention and has produced only marginal success to date in enhancing electrical properties. In U.S. Pat. No. 3,073,785 Angelo disclosed the incorporation of bis(acetylacetonato) copper (II) into a polyimide which resulted in a significant reduction in volume resistivity from 10.sup.17 to 10.sup.12 -10.sup.13 ohm-cm. However, this is still inadequate for bleeding off static charges in space applications and a definite need still exists for a further reduction in the electrical resistivity of polyimide film.
It is therefore an object of the present invention to provide an improvement in the electrical conductivity of linear aromatic polyimides.
Another object of the present invention is a method of preparing high temperature, electrically conductive palladium containing polyimide film.
A further object of the present invention is a method of making palladium ion-containing polyamic acids and ultimately thin, flexible and lightweight palladium containing polyimide film for potential use in space applications.